Land/mobile communication devices, such as portable and mobile two-way radios, are extensively used to provide communication capability in a variety of emergency and non-emergency situations. During an emergency, the communication devices are expected to operate flawlessly, even under severe environmental conditions. Submersibility and protection from the entry of undesired substances is an important consideration in design of submersible communication devices and for achieving highly-reliable communication during inclement weather or when the communication device is utilized at sea.
Generally, a communication device includes a housing for enclosing radio circuit assembly and subassemblies. However, one or more apertures may be formed on the exterior surfaces of the housing for allowing a user to interface with the communication device. For example, user interface apertures may be formed for positioning interface switches. More importantly, the communication device housing usually includes acoustic microphone and speaker apertures to allow transfer of acoustic energy from speaker or into microphone.
Many submersible or otherwise known waterproof communication devices already exist. Conventionally, a number of sealing means, such as pads and gaskets, are utilized for sealing the apertures of the radio housing. Gaskets seal the outer periphery of the housing while individual sealing pads seal apertures formed within the inner periphery of the housing.
A particular problem arises, however, when a microphone aperture is sealed using a sealing pad or a sealing membrane. This is because the sealing membrane may cause excessive acoustic attenuation, hindering transfer of acoustic energy into the microphone, thereby reducing the efficiency of such transfers.
Conventional approaches for preventing entry of undesired substances through the microphone aperture comprise using a long, curved acoustic pipe which extends from a microphone positioned well within the enclosure to attach to the microphone aperture disposed on the housing. In this way, the curved formation of the acoustic pipe substantially prevents entry of water and other undesired substances. The curved pipe approach, however, causes both frequency response deterioration and increased acoustic distortion. Furthermore, strictly speaking, this approach doesn't fully waterproof and seal the communication device. Therefore, there exists a need for a microphone assembly which is fully waterproof and which can be used in a communication device without increasing distortion and acoustic attenuation.